"Research Disclosure, April 1980, Number 192", page 142, discloses a photographic film having a pair of spaced rows of sprocket holes, 8 sprocket holes per imaging area (film frame) on the film, and a leader portion of the film formed with a series of digitally coded areas, some or all of which are perforated for identifying respective photographic characteristics of the film.
Where a photographic camera utilizes such a film as disclosed in "Research Disclosure" and the sprocket holes and/or the coded perforations are desired to be used out, the film must retain, or be retained, its flatness at the location where they are read out. Although a pressure plate usually secured to the back cover of the camera can be utilized to retain the film flat, the pressure plate has its main function to urge the film towards a pair of spaced film guide rails at an exposure station and, therefore, where a read-out device is provided in the camera at such exposure station, there is the possibility that, when and after the leader portion of the film has been wound onto a spool, some or all of the coded perforations would have moved past the read-out device with the consequent failure of the read-out device to generate a output indicative of the data represented by the coded perforations. Where the read-out device is arranged in the camera at a position past the pressure plate, since when the film having been drawn out of the patrone (cartridge) a larger amount than required is wound onto the spool and when the back cover is subsequently closed, the film being sandwiched between the film guide rails and the pressure plate as the back cover is being closed is squeezed to curl, the accurate and faithful reading of the coded perforation can not be performed. The detection by the read-out device is also possible subject to the sprocket holes, and the read-out device may be used, for example, in counting the sprocket holes for the purpose of determination of the length of the film to be advanced.
Moreover, since where the above described film is utilized, the reading of the coded perforations takes place as the film moves past the read-out device, the use of a memory device for storing information read out from the coded perforations is necessary where the camera is to be controlled in dependence on such information. When it comes to the memory device, an electrically operated memory device is desirable in the case of the camera which is generally required to be compact in size and to have an electrically controlled feature. However, even though the memory device is used, the removal of a battery providing a source of electrical power out of the camera results in erasing of the contents stored in the memory device. Accordingly, so far as the camera utilizing the above described film is involved, countermeasures must be taken to avoid the unnecessary erasing of the information once stored in the memory device.
Where as the read-out device an optical read-out device such as disclosed in the above mentioned "Research Disclosure" is utilized, light emitted from a light emitting element passes through the coded perforation or the sprocket holes when they are brought into register with the detection position, but is reflected towards a photo sensor when inperforate areas of the film are brought into register with the detection position, with the consequence that the photo sensor generates a pulse output. However, where means for retaining the film flat is positioned rearwardly of the film, the light that has passed through the coded perforations or the sprocket holes tends to be reflected towards the photo sensor from the surface of the retaining means and, as a result thereof, the difference between the outputs given by the photo sensor when the coded perforation or the sprocket hole has been brought into register with the detection position and when it is not in register with the detection position, respectively, tends to become small to such an extent that the detection of the coded perforation or the sprocket holes becomes difficult. In order to avoid this problem, the U.S. Pat. No. 4,304,480 discloses the pressure plate coated black on one of its surfaces facing the film for the purpose of causing the reflected light to be attenuated. However, since a light emitting element emits an infrared light, a mere black coating of the surface of the pressure plate would not solve the problem effectively and, therefore, a special black pigment effective to absorb the infrared light must be used for the coating.
In the above described film, information represented by the coded perforations may include the film speed, the color temperature of the film, the expiration date of the film and others, and it is desired that a worning can be automatically made in dependence on the information whenever inaccurate and/or improper conditions occur in the camera. By way of example, since the film speed of the film now largely used is ASA 100 or ASA 400, a beginner photographer is generally not accustomed to set to the camera a different film speed other than the usual film speeds and will fail to do so when the film of the different film speed is occasionally loaded in the camera. In addition, considering that the film is available in three types i.e., Type-A (a tungsten type having a color temperature of 3,400 K.), Type-B (a tungsten type having a color temperature of 3,200 K.) and Type-D (a daylight type having a color temperature of 5,500 K.), a photographic picture, when taken under electronic flash lighting condition using any one of the tungsten type films, tends to show an unnatural color.
Furthermore, when it comes to the film of which the expiration date has already expired, not only is the film speed reduced, but also the use of such film is likely to result in deteriorated color presentation. Accordingly, it is desirable to warn the photographer that he or she is currently using the film of which the expiration date has already expired.
Apart from the above discussed matters, in the case where the camera is so designed that, when and after the film has been loaded in the camera, an automatic preparatory winding of the film to bring an initial imaging area (film frame) on the film to the exposure station can be performed in response to the detection of the film loading, the photographer will be nonplused if the film is wound up at a high speed during a period subsequent to the film loading and before the back cover is closed and, in the worst case it may happen, he or she will cut his or her finger by the edge of the film being wound up at the high speed. Therefore, it has long been desired to effect the preparatory winding of the film at a low speed up until the back cover is completely closed.
Further, it has often occurred that the film, some of the imaging areas (film frames) of which have been photographically exposed, is rewound into the patrone or cartridge and then unloaded from the camera for use at a different occasion. For example, after the photographer has taken pictures on 10 consecutive imaging areas out of the maximum available 24 frames of one film with a particular camera and then unloaded it from such particular camera, he will reload the film in such particular camera or a different camera for taking pictures on the remaining unexposed imaging areas. In such case, the reloaded film must be advanced to make the camera's film frame counter to read "11". According to the prior art, the reloaded film must be advanced frame to frame manually by operating a film wind-up lever until the film frame counter show that the eleventh imaging area has brought to the exposure station. This procedure is really inconvenient and time-consuming, and it has long been desired to permit the film to be automatically advanced to the eleventh imaging area if a number "11" is preset to the camera. In addition, for indicating or warning the photographer that the number of the film imaging areas to be advanced which has been preset is inadvertently greater than the number of the film imaging areas to be actually advanced, the camera is desired to have an adequate warning system.